Avulsion fractures are the result of side-to-side (coronal) forces acting on
the finger, putting the collateral ligament under sudden tension. The ligament
is usually stronger than the bone, causing the ligament to avulse a fragment of
bone at its insertion.
Avulsion fractures result in marked joint instability.
If the fracture is not displaced, nonoperative treatment is usually indicated
(buddy taping to the adjacent finger). Displaced fractures, however, must be